INFORMATION-CONTENT OF LONG-EXPOSED DOUBLE STAR IMAGES

With this paper we present the mathematical background for a novel met hod for the deconvolution of longer exposed double star images, merged by seeing and other effects. This method, which was recently presente d in a short paper (Muller and Geyer 1993) makes use of the autocorrel ation of the odd function of the merged, and thus asymmetric two dimen sional double star image profile. We give the mathematical evidence th at digital filtering during the image processing does not influence th e angular distance of the binary components, and that it can be determ ined independently of the brightness difference of the components. The brightness difference itself can be obtained without ambiguity, if it does not exceed 3 mag, and then the distance has been derived before. We further show that the information content of stellar images is gen erally less degraded by seeing effects as was previously supposed. Thu s closer double stars can be resolved and photometrically deconvoluted by the method. By atmospheric disturbances, telescope guiding errors, optical distortions and silhouetting generally the stellar images on astrometric photographs of modern opto-electronic detectors are asymme trically deformed. Therefore, the method yields also better accuracy a nd more adequate results for astrometry, photometry, and also astrospe ctroscopy.